Conventionally, pressure sensors or transducers are mounted within a desired downhole tool or apparatus which is custom built or designed to receive the pressure sensor. These pressure sensors are fixedly or non-removably mounted within the tool at the manufacturing facility or machine shop and shipped to the customer for use in the field. Accordingly, the pressure sensors are required to be calibrated in the shop prior to mounting within the tool.
During use of the tool in the field, the pressure sensor may be exposed to conditions which either damage the pressure sensor or adversely affect the calibration of the pressure sensor. As a result, repair or re-calibration of the pressure sensor may be required. Further, depending upon the conditions encountered downhole, it may be desirable to use a variety of pressure sensors with varying pressure ratings throughout the production or drilling operation. As a result, replacement of the pressure sensor with an alternate pressure sensor may be desirable throughout the production or drilling operation.
In each of these cases, the pressure sensor is not capable of being replaced, repaired or re-calibrated in the field. Rather, the entire tool must be returned to the shop for removal of the pressure sensor from the tool such that the pressure sensor may be repaired, replaced or further calibrated. During this period, the tool is unavailable for use which results in undesirable downtime for the tool and increased costs for the production or drilling operation.
Further, as indicated, the tool is custom designed or built to accept a particular desired pressure sensor for mounting therein. Specifically, the manufacturing facility or machine shop is required to custom build each tool to accept a particular pressure sensor with a desired pressure rating to meet the requirements of each particular customer. As a result, the shop is typically required to keep a relatively large inventory of tools available in order to be in a position to meet the needs of the customer in a timely manner. Further, the shop must be capable of calibrating all of the different types and sizes of tools in which the pressure sensors are mounted.
As a result, removable pressure sensors have been developed. However, none of these removable pressure sensors have been found to be fully satisfactory. Examples of removable pressure sensors include: United Kingdom Patent Application No. GB 2,366,308 A published Mar. 6, 2002 by Ryan Energy Technologies Inc.; U.S. Pat. No. 3,939,705 issued Feb. 24, 1976 to Glotin et. al.; U.S. Pat. No. 4,105,279 issued Aug. 8, 1978 to Glotin et. al.; U.S. Pat. No. 4,506,731 issued Mar. 26, 1985 to Skinner; U.S. Pat. No. 4,582,136 issued Apr. 15, 1986 to Skinner; and U.S. Pat. No. 4,967,853 issued Nov. 6, 1990 to Landry.
In addition, many pressure sensors used downhole have not been found to be fully satisfactory due to a proneness towards de-calibration and failure for several reasons. First, repeated removal and replacement of the pressure sensor tends to stress a metal housing typically surrounding or enclosing at least a part of the pressure sensor which disturbs the calibration of the pressure sensor therein. In addition, the handling of the pressure sensor during its removal and replacement may also adversely affect the calibration of the sensor.
Second, in use, the interior of the metal housing for the pressure sensor is typically exposed to high ambient pressure downhole. Exposure of the pressure sensor to multiple pressure cycles tends to cause a stretching of the metal housing over time which also adversely affects the calibration of the pressure sensor.
Finally, conventional pressure sensors are sealed and held within the metal housing by the use of one or more O-rings so that the pressure sensor may be easily removed from the housing in the event of the failure of the pressure sensor. However, the O-rings themselves are prone to failure and decrease the reliability of the tool and the pressure sensor in the field. For instance, O-rings tend to corrode resulting in a tendency to fail. As well, O-rings permit certain undesirable gases, such as carbon dioxide, to pass therethrough which may adversely affect the electronic components of the pressure sensor.
As a result, there is a need in the industry for an improved pressure sensor for use in a downhole tool or apparatus. Further, there is a need for a replaceable pressure sensor insert which is adapted for removable connection with an insert carrier such as a downhole production or drilling tool or apparatus. Preferably, the pressure sensor insert and the pressure sensor therein address one or more of the disadvantages or undesirable features associated with conventional or known fixed or replaceable pressure sensors as discussed above.